Seems strange to be signed twice to different people, plus the Rosemary signature page has more handwriting on the backside that you can kind of see through the paper. Almost looks like a letter or something (one of the Father Christmas letters?)

Seller seems nice enough. The second signature/dedication is on a loose sheet of stationery laid in, with a third signature on the back ("Mary Dentry" he thinks) dated 1974. Sounds like "Cookie" was gathering autographs, possibly at an event of some sort. The current seller bought the book at a bookfair in 2002, so he doesn't have much provenance on it, but I think the signatures look reasonable.